A wireless transmit/receive unit (WTRU), which in some cases may be a user equipment (UE), often undergoes handover during communication. The handover may occur from a trusted non-Third Generation Partnership Project (non-3GPP) Internet protocol (IP) access system to a 3GPP access system (evolved universal terrestrial radio access network (E-UTRAN)), and from a 3GPP access system (E-UTRAN) to a trusted non-3GPP IP access system.
In addition, the handover may occur during a roaming or non-roaming scenario. FIG. 1 shows an example network architecture 100. As defined in FIG. 1 and hereafter, the following reference points apply:
S2a: Provides the user plane with related control and mobility support between trusted non 3GPP IP access and the packet data network (PDN) Gateway (GW).
S2b: Provides the user plane with related control and mobility support between the evolved packet data gateway (ePDG) and the PDN GW.
S2c: Provides the user plane with related control and mobility support between a WTRU and the PDN GW. This reference point is implemented over trusted and/or untrusted non-3GPP Access, and/or 3GPP access.
S5: Provides user plane tunneling and tunnel management between Serving GW and PDN GW. It is used for Serving GW relocation due to mobility and in case the Serving GW needs to connect to a non-collocated PDN GW for the required PDN connectivity.
S6a: This interface is defined between mobility management entity (MME) and home subscriber server (HSS) for authentication and authorization.
S6c: The reference point between PDN GW in a home public land mobile network (HPLMN) and a 3GPP authentication, authorization and accounting (AAA) server for mobility related authentication if needed. This reference point may also be used to retrieve and request storage of mobility parameters.
S6d: The reference point between the Serving Gateway in a visited public land mobile network (VPLMN) and a 3GPP AAA Proxy for mobility related authentication if needed. This reference point may also be used to retrieve and request storage of mobility parameters.
S7: Provides transfer of quality of service (QoS) policy and charging rules from policy and charging rules function (PCRF) to policy and charging enforcement point (PCEF). The allocation of the PCEF is for further study (FFS).
S8b: The roaming interface in case of roaming with home routed traffic. It provides the user plane with related control between Gateways in the VPLMN and the HPLMN.
S9: Indicates the roaming variant of the S7 reference point for the enforcement in the VPLMN of dynamic control policies from the HPLMN.
SGi: The reference point between the PDN Gateway and the packet data network. The packet data network may be an operator external public or private packet data network or an intra operator packet data network, e.g. for provision of IP multimedia subsystem (IMS) services. This reference point corresponds to Gi and Wi functionalities and supports any 3GPP and non-3GPP access systems.
Wa*: Connects the untrusted non-3GPP IP access with the 3GPP AAA server/proxy and transports access authentication, authorization and charging-related information in a secure manner.
Ta*: Connects the trusted non-3GPP IP Access with the 3GPP AAA server/proxy and transports access authentication, authorization, mobility parameters and charging-related information in a secure manner.
Wd*: Connects the 3GPP AAA proxy, possibly via intermediate networks, to the 3GPP AAA server. Differences compared to Wd are FFS.
Wm*: This reference point is located between 3GPP AAA Server/Proxy and ePDG and is used for AAA signaling, (transport of mobility parameters, tunnel authentication and authorization data).
Wn*: This is the reference point between the untrusted Non-3GPP IP Access and the ePDG. Traffic on this interface for an initiated tunnel has to be forced towards ePDG.
Wx*: This reference point is located between 3GPP AAA Server and HSS and is used for transport of authentication data.
Usage of S6, S8 and S9 for providing a visited network with static/dynamic policies is under consideration. It is also under consideration if the two depicted S7 interfaces are different. The S1 interface for the E-UTRAN is the same for both the architectures.
FIG. 2 is a signal diagram 200 of a conventional handover from a 3GPP Access UTRAN to a trusted non-3GPP IP Access network. The handover scenario involves the S2a reference point and includes scenarios using PMIPv6 and mobile IP4 (MIP4) with foreign agent care-of-address (FACoA). For the FACoA mode of MIPv4, it may be considered that the S2a runs between the FA in the non-3GPP system and the PDN GW in the HPLMN. While the WTRU is connected in the 3GPP access system, PMIPv6 or general packet radio service (GPRS) tunneling protocol (GTP) is used over S5. The dual stack mobile IPv6 (DSMIPv6) protocol used over S2c is compliant to the DSMIPv6 specification over the S2a interface with PMIPv6 for a non-roaming scenario. The signaling is as follows:
1. The WTRU discovers the trusted non-3GPP IP access and decides to initiate handover from the currently used UTRAN access to the discovered trusted non-3GPP IP access system. The mechanism that aids the WTRU to discover trusted non-3GPP IP access, are specified in section on Network Discovery and Selection. At this point both uplink and downlink user data is transmitted via the following: Bearers between WTRU and source access network, GTP tunnel(s) between source 3GPP access network, Serving GW and PDN GW.
2. The initial Non-3GPP access specific L2 procedures are performed. These procedures are Non-3GPP access specific and are outside the scope of 3GPP.
3. The EAP authentication procedure is initiated and performed involving the WTRU, trusted Non-3GPP IP Access and the 3GPP AAA Server. In the roaming case, there may be several AAA proxies involved. As part of the authentication procedure, the IP address of the PDN GW that needs to be used is conveyed to PMA in the trusted Non-3GPP IP Access.
4. After successful authentication and authorization, the L3 attach procedure is triggered.
5. PMA function of trusted Non-3GPP IP Access sends Proxy Binding Update message to PDN GW.
6. The PDN GW processes the proxy binding update and creates a binding cache entry for the WTRU. The PDN GW allocates IP address for the WTRU. The PDN GW then sends a proxy binding acknowledgement to the PMA function in Trusted Non-3GPP IP Access, including the IP address(s) allocated for the WTRU. The IP address allocated is same as that was assigned to WTRU before over 3GPP access.
7. The PMIPv6 tunnel is set up between the Trusted Non-3GPP IP Access and the PDN GW.
8. L3 attach procedure is completed. IP connectivity between the WTRU and the PDN GW is set for uplink and downlink direction over the trusted non-3GPP IP access.
9. Resource clean up for the source 3GPP access is initiated by performing the necessary procedures based on the procedures specified in the 3GPP standard. PDN GW should retain the IP connectivity for the WTRU.
FIG. 3 is a signal diagram 300 of a conventional trusted non-3GPP IP access to E-UTRAN with PMIPv6 handover for a non-roaming scenario. The signaling is as follows:
1. The UE uses a trusted non-3GPP access system and is being served by PDN GW.
2. The UE discovers the E-UTRAN access system and determines to transfer its current sessions, (i.e., handover), from the currently used non-3GPP access system to the discovered E-UTRAN access system. The mechanisms that aid the UE to discover the E-UTRAN access system.
3. The UE sends an Attach Request which is routed by E-UTRAN to an MME instance in the EPS.
4. The MME contacts the HSS and authenticates the UE. As part of the authentication procedure, the IP address of the PDN GW that needs to be used is conveyed to the MME.
5. After successful authentication, the MME performs a location update procedure with the HSS.
6. The MME selects a serving GW and sends a Create Default Bearer Request (IMSI, MME Context ID) message to the selected Serving GW. It also includes the IP address of the PDN GW which was provided by the HSS.
7. Based on the Create Default Bearer Request from the MME, the Serving GW initiates the PMIPv6 registration procedure towards the PDN GW by sending a Proxy Binding Update.
8. The PDN GW responds with a Proxy Binding ACK and updates its mobility binding which effectively switches the PMIPv6 tunnel from the non-3GPP access network to the Serving GW. In the proxy Binding ACK, the PDN GW replies with the same IP address or prefix that was assigned to the UE earlier. A PMIPv6 tunnel exists now between PDN GW and Serving GW.
9. The Serving GW returns a Create Default Bearer Response message to the MME. This message also includes the IP address of the UE. This message also serves as an indication to the MME that the binding has been successful.
10. The MME sends an Attach Accept message to UE through E-UTRAN.
11. Radio-bearer and S1-U bearer is setup.
12. The UE resumes data communication over E-UTRAN.
FIG. 4 is a signal diagram 400 of a conventional E-UTRAN to trusted non-3GPP IP access with PMIPv6 handover for a non-roaming scenario. The signaling is as follows:
1. The UE uses a trusted non-3GPP access system and is being served by PDN GW.
2. The UE discovers the E-UTRAN access system and determines to transfer its current sessions (i.e. handover) from the currently used non-3GPP access system to the discovered E-UTRAN access system. The mechanisms that aid the UE to discover the E-UTRAN access system are specified in the 3GPP standards.
3. The UE sends an Attach Request which is routed by E-UTRAN to an MME instance in the EPS as specified in TS 23.401.
4. The MME contacts the HSS and authenticates the UE. As part of the authentication procedure, the IP address of the PDN GW that needs to be used is conveyed to the MME.
5. After successful authentication, the MME performs a location update procedure with the HSS.
6. The MME selects a serving GW and sends a Create Default Bearer Request (IMSI, MME Context ID) message to the selected Serving GW. It also includes the IP address of the PDN GW which was provided by the HSS.
7. Based on the Create Default Bearer Request from the MME, the Serving GW initiates the PMIPv6 registration procedure towards the PDN GW by sending a Proxy Binding Update.
8. The PDN GW responds with a Proxy Binding ACK and updates its mobility binding which effectively switches the PMIPv6 tunnel from the non-3GPP access network to the Serving GW. In the proxy Binding ACK, the PDN GW replies with the same IP address or prefix that was assigned to the UE earlier. A PMIPv6 tunnel exists now between PDN GW and Serving GW.
9. The Serving GW returns a Create Default Bearer Response message to the MME. This message also includes the IP address of the UE. This message also serves as an indication to the MME that the binding has been successful.
10. The MME sends an Attach Accept message to UE through E-UTRAN.
11. Radio-bearer and S1-U bearer is setup.
12. The UE resumes data communication over E-UTRAN.
FIG. 5 is a signal diagram 500 of a conventional procedure for implementing a handover from a trusted non-3GPP IP access system with DSMIPv6 over S2c to a 3GPP access system in a conventional non-roaming scenario. In this scenario, the session starts in a trusted non-3GPP access system, (e.g., E-UTRAN), using DSMIPv6 in a non roaming scenario. Subsequently, the session hands over to a 3GPP access system. The signaling is as follows:
1. The UE uses a trusted non-3GPP access system. It has a DSMIPv6 session with the PDN GW.
2. The UE discovers the 3GPP access system and determines to handover from the currently used trusted non-3GPP access system to the discovered 3GPP access system. The mechanisms that aid the UE discover the 3GPP access system are specified in the 3GPP standards.
3. The UE sends an Attach Request which is routed by 3GPP to an MME instance in the EPC.
4. The MME contacts the HSS/3GPP AAA and authenticates the UE. As part of the authentication procedure, the IP address of the PDN GW that needs to be used in 3GPP access is conveyed to the MME.
5. After successful authentication, the MME performs the location update procedure with HSS.
6. The MME selects a Serving GW and sends a Create Default Bearer Request (including IMSI, MME Context ID, and PDN GW IP address) message to the selected Serving GW.
7. a) For IETF based S5, the Serving GW initiates the PMIPv6 registration procedure towards the PDN GW by sending a Proxy Binding Update. If the NAI of the user is not included in step 6, the Serving GW has to derive it by other means.
b) For GTP based S5, the Serving GW sends a Create Bearer Request message to the PDN GW.
8. a) For IETF based S5, the PDN GW responds with a Proxy Binding Ack and updates its mobility binding which effectively switches the DSMIPv6 tunnel from the non-3GPP access network to the PMIPv6 tunnel to the Serving GW. In the proxy Binding Ack, the PDN GW includes the same IP address or prefix that was assigned to the UE earlier.
b) For GTP based S5, the PDN GW responds with a Create Bearer Response message to the Serving GW. The Create Bearer Response contains the same IP address or prefix that was assigned to the UE earlier.
9. The Serving GW returns a Create Default Bearer Response message to the MME. This message also includes the IP address of the UE. This message also serves as an indication to the MME that the binding has been successful.
10. The MME sends an Attach Accept message to UE through 3GPP access. The 3GPP access system initiates the radio bearer setup procedure. The 3GPP access system responds with an Attach Complete message.
11. The UE may send a BU to the PDN GW to de-register its DSMIPv6 binding that was created while the UE was in non-3GPP access system.
FIG. 6 is a signal diagram 600 of a conventional procedure for implementing a handover from a 3GPP access system to a trusted Non-3GPP IP access system with DSMIPv6 over S2c in a non-roaming scenario. In this scenario, the session starts in 3GPP access, (e.g., E-UTRAN), using PMIPv6 or GTP over S5 or no S5 is used (co-located Serving GW and PDN GW). The session hands over to the trusted non-3GPP access system that does not use PMIPv6 where the UE will receive a different prefix than the one it was using in 3GPP access system. The UE subsequently initiates DSMIPv6 with the same PDN GW to maintain the IP session. The signaling is as follows:
1. The UE uses a 3GPP access system. It has an IP address that is supported over S5 interface.
2. At this point the UE decides to initiate non-3GPP access procedure. The decision is based on any number of reasons e.g. local policies of the UE.
3. The UE performs access authentication and authorization in the non-3GPP access system. The 3GPP AAA server authenticates and authorizes the UE for access in the non-3GPP system. Note that PDN GW selection and retrieval for host based mobility is still an FFS.
4. The non-3GPP access system is not PMIPv6 capable or it decides not to use PMIPv6. Therefore, the UE gets an IP address that is different from the IP address it was using in 3GPP access system. Since the UE obtains an IP address that is not the same as the address from 3GPP system, the UE decides to initiate DSMIPv6 procedures to maintain its IP sessions.
5. The UE may discover PDN GW address using MIPv6 bootstrapping procedures.
6. The UE may also perform IKEv2 and IPSec SA establishment with the PDN GW that was discovered at step 5. This happens if RFC 4877 is used to establish SA between the UE and the PDN GW. This step may involve authentication and authorization by the 3GPP AAA system.
7. The UE sends a DSMIPv6 BU message to the PDN GW to register its CoA. The PDN GW authenticates and authorizes the UE sends back a BA including the IP address (home address) which the UE was using in the 3GPP access.
8. The UE continues with IP service using the same IP address.
It would therefore be beneficial to provide a method and apparatus that manages system resources after a successful handover.